This invention is directed to a position compensation mechanism for a movie camera having inner and outer housings and, in particular, to a position compensation mechanism that maintains the orientation of the film gate positioned on the inner housing, with respect to the camera optic on the outer housing when the movie camera is displaced.
A variety of motion picture cameras of the professional type are presently available. One type of movie camera includes an inner housing which supports a film transport mechanism for moving the film and a film gate and shutter for exposing consecutive frames of the film so that the film is exposed to light. The inner camera housing is generally mounted in an outer camera housing which is adapted to support the photographic optics (lenses) of the camera. The photographic optics are adjustable with respect to the film gate and shutter so that proper focusing can be made. However, where the motion picture camera is adapted to record sound as well as visual scenes, it is preferable for the inner housing to be properly mounted within the outer housing so that sounds are not transmitted from the inner housing to the outer housing.
Accordingly, mountings have been developed which substantially dampen sounds created by the internal mechanism to the outer housing. One such type of mounting is disclosed in applicant's co-pending U.S. patent application Ser. No. 174,063 entitled Adjustable Mountings for A Movie Camera, filed July 30, 1980 which is hereby incorporated by reference as if fully set forth herein. Such sound damping mountings are generally resilient in nature so that when the camera is tilted or displaced for properly filming the desired scenes, the inner housing will be displaced with respect to the outer housing. Hence, the film gate and shutter, which are mounted on the inner housing, will also be displaced relative to the photographic optics (lenses) of the movie camera and the camera will move out of focus. The positioning of the film gate with respect to the photographic optics and the distance of the film gate and shutter to the supporting surface of the photographic optics define a predetermined orientation when the focusing of the camera is optimized. However, this orientation will be changed whenever the camera is tilted, thereby impairing the picture definition or focusing. The problem is particularly acute in vertical tilting of the motion picture camera. Specifically, the focal plane distance, namely the distance from the support surface of the photograph optics to the plane defined by the film passing through the film gate, is a factor that is most significant in obtaining optimum focusing of the lens.
As disclosed in applicant's co-pending U.S. patent application, Ser. No. 174,063, the mountings which support the inner housing on the outer housing are adjustable to allow for proper positioning. However, continuous manual adjustment of the lenses or mountings would be required to keep the camera in focus for filming a scene wherein the camera is to be selectively repositioned. Accordingly, a position compensation mechanism coupled intermediate the inner housing and the outer housing which will substantially maintain the position of the inner housing with respect to the outer housing so that the film gate maintains its orientation with respect to the camera optics is desired.